The overall purpose of this proposal is to develop novel therapeutic approaches to prevent type 1 diabetes by utilizing catalytic RNAs or ribozymes. Type 1 diabetes is a T cell mediated autoimmune disease. The regulatory mechanisms that underlie the development and activation of pathogenic T cells in diabetes are not clear. Previous studies have shown that a breakdown of tolerance and an imbalance of Th1 vs. Th2 type of cytokines with a skewing toward the development of Th1 cells may be involved in the induction and development of type 1 diabetes. It is hypothesized that therapeutic treatment of the disease may be achieved using ribozymes to black the development of diabetogenic Th1 cells or to black adhesion molecules to induce peripheral tolerance of T cells. Ribozymes are enzymatic RNAs that can be engineered to site-specifically cleave targeted RNA and have been effectively used in cell culture and in animal models. For Specific Aim 1, hammerhead ribozymes will first be developed and the most effective ribozymes will then be expressed in T-cells and bone marrow stem cells. Functional expression of the ribozymes will be assayed in vito. Effective combinations of ribozymes and expression systems will be further tested by incorporation into murine retroviral or adeno associated viral (AAV) vectors for delivery into T-cells, bone marrow stem cells and pancreatic islets. In vivo testing of these genetically altered cells in Specific Aim 2 will be carried out in non-obese diabetic (NOB) mice. These studies will critically examine whether or not down regulation of the proposed targets by ribozymes has potential for treating type 1 diabetes.